Session NN. Noise IV: Outdoor Sound Propagation: A Special Workshop

Abstract

The nature of sound propagation in the outdoor environment is an important consideration in the prediction of the noise impact from highways, airports, and railroads. Current noise prediction methods do not adequately account for the manner in which sound is attenuated with distance over open ground or through vegetation. A considerable amount of research has been conducted on outdoor sound propagation; however, a review of the literature shows that there are large discrepancies between various researchers for both open ground propagation and for propagation through forests. The results of theoretical analyses for the open ground case vary, depending on the boundary condition assumption. The assumption of a locally reacting ground surface results in a solution which appears to be valid; however, when the ground is treated as an elastic medium a different result is obtained. An additional deviation is obtained when the ground is treated as a layered elastic medium. It appears that the results of the various experimental studies may have been dependent on the particular test methods used and other factors. For both the experimental and theoretical studies there is no reason to believe at this point that any one approach is more valid than another. The purpose of this workshop session is to assemble the various scientists who have worked in the field of outdoor sound propagation to attempt to resolve the discrepancies between the studies and to formulate future research plans. The session will begin with several formal presentations of papers followed by a round table discussion. Although specific persons have been invited to this session, we welcome participation by anyone who has an interest in the subject.